Various types of continuously operating shot-blasting machines are known, such devices being used for drummable workpieces which are to be blasted on all sides wherein, for example, plate conveyors with turning arrangements or step-like vibrating conveyors are used for the transportation of the workpieces through a blasting chamber. Preferably, however, such machines are made as continuous drum blasting machines with a rotating drum or a swiveling drum (as shown, respectively, in German Pat. No. 109,648 and German Offenlegungsschrift No. 24 24 086), the drum constituting the blasting chamber. The feed of the workpieces is achieved by screw conveyors disposed in the drum or by conical drums in which the drums can be slanted in the direction of conveyance. Also, continuous blasting machines with a feed and a discharge drum and a belt trough disposed in the radiation chamber for the revolution of the workpieces has been known as shown in German Offenlegungsschriften No. 20 16 429.
In all of these continuous shot-blasting machines, great differences in operation occur in the rate of delivery of the incoming articles, with the result that variable quantities of different types of workpieces must be blasted in succession. Such variations occur, for example, when the blasting apparatus is in direct connection with automatic molding and casting installations which have a sporadic output, or in the event that breakdowns develop in preceding treatment steps. These variations in throughflow, which are to be expected, can occur according to experience in a ratio in the order of 1:20, and the inflow can drop to zero from time to time. Whenever the adjustment of the blasting machine is not adapted to such differences in throughput, then the danger exists that the workpieces can either be over or under blasted, or that excessive wear and tear can occur in the parts of the machine such as, for example, the blasting medium impellers and the protective linings, or that an unnecessarily great consumption of the blasting medium occurs. In any of these cases, it will be clear that the machine operates uneconomically.